Face Detection, Tracking, and Recognition for a Visual Prosthesis

ABSTRACT

The present invention is a system for detecting, tracking and recognizing human faces in a visual prosthesis. In a visual prosthesis, the input camera is always higher resolution than the electrode array providing percepts to the subject. It is advantageous to detect, track and recognize human faces. Then information can be provided to the subject by highlighting the face in the visual scene, providing auditor or vibratory notice that a human face is in the visual scene, looking up the face in a database to state the name of the person in the visual scene, otherwise communication id like providing a custom vibratory pattern corresponding to known individuals (like custom ring tones associated with caller ID) or automatically zooming in on a face to aid the subject in identifying the face.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is claims priority to U.S. Provisional Application61/515,794, filed Aug. 5, 2011, for Face Detection Tracking andRecognition for a Visual Prosthesis, the disclosure of which isincorporated by reference.

FIELD OF THE INVENTION

The present invention is generally directed to neural stimulation andmore specifically to improved usability of a visual prosthesis by usingfacial detection, tracking and recognition.

BACKGROUND OF THE INVENTION

In 1755 LeRoy first created a visual perception through electricalstimulation. Ever since, there has been a fascination with electricallyelicited visual perception. The general concept of electricalstimulation of retinal cells to produce these flashes of light orphosphenes has been known for quite some time. Based on these generalprinciples, some early attempts at devising a prosthesis for aiding thevisually impaired have included attaching electrodes to the head oreyelids of patients. While some of these early attempts met with somelimited success, these early prosthetic devices were large, bulky andcould not produce adequate simulated vision to truly aid the visuallyimpaired.

In the early 1930's, Foerster investigated the effect of electricallystimulating the exposed occipital pole of one cerebral hemisphere. Hefound that, when a point at the extreme occipital pole was stimulated,the patient perceived a small spot of light directly in front andmotionless (a phosphene). Subsequently, Brindley and Lewin (1968)thoroughly studied electrical stimulation of the human occipital(visual) cortex. By varying the stimulation parameters, theseinvestigators described in detail the location of the phosphenesproduced relative to the specific region of the occipital cortexstimulated. These experiments demonstrated: (1) the consistent shape andposition of phosphenes; (2) that increased stimulation pulse durationmade phosphenes brighter; and (3) that there was no detectableinteraction between neighboring electrodes which were as close as 2.4 mmapart.

As intraocular surgical techniques have advanced, it has become possibleto apply stimulation on small groups and even on individual retinalcells to generate focused phosphenes through devices implanted withinthe eye itself. This has sparked renewed interest in developing methodsand apparati to aid the visually impaired. Specifically, great efforthas been expended in the area of intraocular visual prosthesis devicesin an effort to restore vision in cases where blindness is caused byphotoreceptor degenerative retinal diseases; such as retinitispigmentosa and age related macular degeneration which affect millions ofpeople worldwide.

Neural tissue can be artificially stimulated and activated by prostheticdevices that pass pulses of electrical current through electrodes onsuch a device. The passage of current causes changes in electricalpotentials across visual neuronal membranes, which can initiate visualneuron action potentials, which are the means of information transfer inthe nervous system.

Based on this mechanism, it is possible to input information into thenervous system by coding the sensory information as a sequence ofelectrical pulses which are relayed to the nervous system via theprosthetic device. In this way, it is possible to provide artificialsensations including vision.

One typical application of neural tissue stimulation is in therehabilitation of the blind. Some fauns of blindness involve selectiveloss of the light sensitive transducers of the retina. Other retinalneurons remain viable, however, and may be activated in the mannerdescribed above by placement of a prosthetic electrode device on theinner (toward the vitreous) retinal surface (epiretinal). This placementmust be mechanically stable, minimize the distance between the deviceelectrodes and the visual neurons, control the electronic fielddistribution and avoid undue compression of the visual neurons.

In 1986, Bullara (U.S. Pat. No. 4,573,481) patented an electrodeassembly for surgical implantation on a nerve. The matrix was siliconewith embedded iridium electrodes. The assembly fit around a nerve tostimulate it.

Dawson and Radtke stimulated cat's retina by direct electricalstimulation of the retinal ganglion cell layer. These experimentersplaced nine and then fourteen electrodes upon the inner retinal layer(i.e., primarily the ganglion cell layer) of two cats. Their experimentssuggested that electrical stimulation of the retina with 30 to 100 μAcurrent resulted in visual cortical responses. These experiments werecarried out with needle-shaped electrodes that penetrated the surface ofthe retina (see also U.S. Pat. No. 4,628,933 to Michelson).

The Michelson '933 apparatus includes an array of photosensitive deviceson its surface that are connected to a plurality of electrodespositioned on the opposite surface of the device to stimulate theretina. These electrodes are disposed to form an array similar to a “bedof nails” having conductors which impinge directly on the retina tostimulate the retinal cells. U.S. Pat. No. 4,837,049 to Byers describesspike electrodes for neural stimulation. Each spike electrode piercesneural tissue for better electrical contact. U.S. Pat. No. 5,215,088 toNorman describes an array of spike electrodes for cortical stimulation.Each spike pierces cortical tissue for better electrical contact.

The art of implanting an intraocular prosthetic device to electricallystimulate the retina was advanced with the introduction of retinal tacksin retinal surgery. De Juan, et al. at Duke University Eye Centerinserted retinal tacks into retinas in an effort to reattach retinasthat had detached from the underlying choroid, which is the source ofblood supply for the outer retina and thus the photoreceptors. See,e.g., E. de Juan, et al., 99 Am. J. Ophthalmol. 272 (1985). Theseretinal tacks have proved to be biocompatible and remain embedded in theretina, and choroid/sclera, effectively pinning the retina against thechoroid and the posterior aspects of the globe. Retinal tacks are oneway to attach a retinal electrode array to the retina. U.S. Pat. No.5,109,844 to de Juan describes a flat electrode array placed against theretina for visual stimulation. U.S. Pat. No. 5,935,155 to Humayundescribes a retinal prosthesis for use with the flat retinal arraydescribed in de Juan.

Each person's response to neural stimulation differs. In the case ofretinal stimulation, a person's response varies from one region of theretina to another. In general, the retina is more sensitive closer tothe fovea. Any stimulation, less than the threshold of perception, isineffective. Stimulation beyond a maximum level will be painful andpossibly dangerous to the patient. It is therefore, important to map anyvideo image to a range between the minimum and maximum for eachindividual electrode. With a simple visual prosthesis, it is possible toadjust the stimulation manually by stimulating and questioning thepatient. As resolution increases, it is tedious or impossible to adjusteach electrode by stimulating and eliciting a patient response.

A manual method of fitting or adjusting the stimulation levels of anauditory prosthesis is described in U.S. Pat. No. 4,577,642, Hochmair etal. Hochmair adjusts the auditory prosthesis by having a user compare areceived signal with a visual representation of that signal.

A more automated system of adjusting an auditory prosthesis using middleear reflex and evoked potentials is described in U.S. Pat. No.6,157,861, Faltys et al. An alternate method of adjusting an auditoryprosthesis using the stapedius muscle is described in U.S. Pat. No.6,205,360, Carter et al. A third alternative using myogenic evokedresponse is disclosed in U.S. Pat. No. 6,415,185, Maltan.

U.S. Pat. No. 6,208,894, Schulman describes a network of neuralstimulators and recorders implanted throughout the body communicatingwirelessly with a central control unit. U.S. Pat. No. 6,522,928,Whitehurst, describes an improvement on the system described in Schulmanusing function electro stimulation also know as adaptive deltamodulation to communicate between the implanted devices and the centralcontrol unit.

Even with all of those technical improvements, it is difficult orimpossible for a subject using a visual prosthesis to detect track andrecognize faces. This often causes social difficulties as the blindsubject cannot look directly at the person as they interact or interpretcommon facial features and head movements which aid in communication.

SUMMARY OF THE INVENTION

The present invention is a system for detecting, tracking andrecognizing human faces in a visual prosthesis system. In a visualprosthesis, the input camera is always higher resolution than theelectrode array providing percepts to the subject. It is advantageous toelectronically detect, track and recognize human faces at this higherresolution. This information can be provided to the subject byhighlighting the face in the visual scene, providing auditory orvibratory notice that a human face is in the visual scene, looking upthe face in a database to identify and annunciate the name of the personin the visual scene or otherwise communication the identity of theperson like providing a custom vibratory pattern corresponding to knownindividuals (like custom ring tones associated with caller ID), orautomatically zooming in on a face to aid the subject in identifying theface.

Additional information obtainable through electronic video processingcan be a significant asset, particularly in social situations. Thesystem can inform the subject if the other person in the visual scene islooking directly at them, to the side or away. Image processing maydetermine if the other person is happy or sad, stationary or moving,moving closer or farther away, nodding or shaking their head. The systemcan provide the visual prosthesis subject with basic facial attributes,such as gender, age or ethnicity.

These features can be provided automatically and continuously or can beuser activated by a user command. As an example, blind people rely moreon their hearing than sighted people. They may find a constant stream ofauditory information distracting. Hence a button or gesture may beprovided to activate auditory or other cues regarding face recognition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the implanted portion of the preferredvisual prosthesis.

FIG. 2 is a side view of the implanted portion of the preferred visualprosthesis showing the strap fan tail in more detail.

FIG. 3 shows the components of a visual prosthesis fitting system.

FIG. 4 is a flowchart showing facial detection.

FIG. 5 is a set of three flowcharts equating face detection response tosquare localization.

FIG. 6 is a flowchart showing the process of face detection.

FIG. 7 is a flowchart showing the process of face cueing.

FIG. 8 is a flowchart showing the process of face annunciation.

FIG. 9 is a flowchart showing the process of facial characteristicdetermination.

FIG. 10 a shows a LOSS OF SYNC mode.

FIG. 10 b shows an exemplary block diagram of the steps taken when VPUdoes not receive back telemetry from the Retinal stimulation system.

FIG. 10 c shows an exemplary block diagram of the steps taken when thesubject is not wearing Glasses.

FIGS. 11-1, 11-2, 11-3 and 11-4 show an exemplary embodiment of a videoprocessing unit. FIG. 11-1 should be viewed at the left of FIG. 11-2.FIG. 11-3 should be viewed at the left of FIG. 11-4. FIGS. 11-1 and 11-2should be viewed on top of FIGS. 11-3 and 14-4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is of the best mode presently contemplated forcarrying out the invention. This description is not to be taken in alimiting sense, but is made merely for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe determined with reference to the claims.

An aspect of the invention is method of aiding a visual prosthesissubject including detecting a face in the subject's visual scene; andproviding cues to the subject regarding a detected face. The cue mayinclude sound, vibration, stating a name associated with the detectedface, highlighting the detected face, zooming in on the detected face,or tactile feedback. The method may further include looking up thedetected face in a look up table to provide a name associated with thedetected face. The cue may further include an indication of if the faceis looking toward the subject, to the side or looking away. A furtheraspect of the invention is including information about a facialcharacteristic in the cue. Facial characteristics may include gender,size, distance, head movement, or other body motion. All of thesecharacteristics are controllable by the subject through controls on thevideo processing unit worn on the body.

FIGS. 1 and 2 present the general structure of a visual prosthesis usedin implementing the invention.

FIG. 1 shows a perspective view of the implanted portion of thepreferred visual prosthesis. A flexible circuit 1 includes a flexiblecircuit electrode array 10 which is mounted by a retinal tack (notshown) or similar means to the epiretinal surface. The flexible circuitelectrode array 10 is electrically coupled by a flexible circuit cable12, which pierces the sclera and is electrically coupled to anelectronics package 14, external to the sclera.

The electronics package 14 is electrically coupled to a secondaryinductive coil 16. Preferably the secondary inductive coil 16 is madefrom wound wire. Alternatively, the secondary inductive coil 16 may bemade from a flexible circuit polymer sandwich with wire traces depositedbetween layers of flexible circuit polymer. The secondary inductive coilreceives power and data from a primary inductive coil 17, which isexternal to the body. The electronics package 14 and secondary inductivecoil 16 are held together by the molded body 18. The molded body 18holds the electronics package 14 and secondary inductive coil 16 end toend. The secondary inductive coil 16 is placed around the electronicspackage 14 in the molded body 18. The molded body 18 holds the secondaryinductive coil 16 and electronics package 14 in the end to endorientation and minimizes the thickness or height above the sclera ofthe entire device. The molded body 18 may also include suture tabs 20.The molded body 18 narrows to form a strap 22 which surrounds the scleraand holds the molded body 18, secondary inductive coil 16, andelectronics package 14 in place. The molded body 18, suture tabs 20 andstrap 22 are preferably an integrated unit made of silicone elastomer.Silicone elastomer can be formed in a pre-curved shape to match thecurvature of a typical sclera. However, silicone remains flexible enoughto accommodate implantation and to adapt to variations in the curvatureof an individual sclera. The secondary inductive coil 16 and molded body18 are preferably oval shaped. A strap 22 can better support an ovalshaped coil. It should be noted that the entire implant is attached toand supported by the sclera. An eye moves constantly. The eye moves toscan a scene and also has a jitter motion to improve acuity. Even thoughsuch motion is useless in the blind, it often continues long after aperson has lost their sight. By placing the device under the rectusmuscles with the electronics package in an area of fatty tissue betweenthe rectus muscles, eye motion does not cause any flexing which mightfatigue, and eventually damage, the device.

FIG. 2 shows a side view of the implanted portion of the visualprosthesis, in particular, emphasizing the fan tail 24. When implantingthe visual prosthesis, it is necessary to pass the strap 22 under theeye muscles to surround the sclera. The secondary inductive coil 16 andmolded body 18 must also follow the strap 22 under the lateral rectusmuscle on the side of the sclera. The implanted portion of the visualprosthesis is very delicate. It is easy to tear the molded body 18 orbreak wires in the secondary inductive coil 16. In order to allow themolded body 18 to slide smoothly under the lateral rectus muscle, themolded body 18 is shaped in the faun of a fan tail 24 on the endopposite the electronics package 14. The strap 22 further includes ahook 28 the aids the surgeon in passing the strap under the rectusmuscles.

Referring to FIG. 3, a Fitting System (FS) may be used to configure andoptimize the visual prosthesis (3) of the Retinal Stimulation System(1).

The Fitting System may comprise custom software with a graphical userinterface (GUI) running on a dedicated laptop computer (10). Within theFitting System are modules for performing diagnostic checks of theimplant, loading and executing video configuration files, viewingelectrode voltage waveforms, and aiding in conducting psychophysicalexperiments. A video module can be used to download a videoconfiguration file to a Video Processing Unit (VPU) (20) and store it innon-volatile memory to control various aspects of video configuration,e.g. the spatial relationship between the video input and theelectrodes. The software can also load a previously used videoconfiguration file from the VPU (20) for adjustment.

The Fitting System can be connected to the Psychophysical Test System(PTS), located for example on a dedicated laptop (30), in order to runpsychophysical experiments. In psychophysics mode, the Fitting Systemenables individual electrode control, permitting clinicians to constructtest stimuli with control over current amplitude, pulse-width, andfrequency of the stimulation. In addition, the psychophysics moduleallows the clinician to record subject responses. The PTS may include acollection of standard psychophysics experiments developed using forexample MATLAB (MathWorks) software and other tools to allow theclinicians to develop customized psychophysics experiment scripts.

Any time stimulation is sent to the VPU (20), the stimulation parametersare checked to ensure that maximum charge per phase limits, chargebalance, and power limitations are met before the test stimuli are sentto the VPU (20) to make certain that stimulation is safe.

Using the psychophysics module, important perceptual parameters such asperceptual threshold, maximum comfort level, and spatial location ofpercepts may be reliably measured.

Based on these perceptual parameters, the fitting software enablescustom configuration of the transformation between video image andspatio-temporal electrode stimulation parameters in an effort tooptimize the effectiveness of the visual prosthesis for each subject.

The Fitting System laptop (10) is connected to the VPU (20) using anoptically isolated serial connection adapter (40). Because it isoptically isolated, the serial connection adapter (40) assures that noelectric leakage current can flow from the Fitting System laptop (10).

As shown in FIG. 3, the following components may be used with theFitting System according to the present disclosure. A Video ProcessingUnit (VPU) (20) for the subject being tested, a Charged Battery (25) forVPU (20), Glasses (5), a Fitting System (FS) Laptop (10), aPsychophysical Test System (PTS) Laptop (30), a PTS CD (not shown), aCommunication Adapter (CA) (40), a USB Drive (Security) (not shown), aUSB Drive (Transfer) (not shown), a USB Drive (Video Settings) (notshown), a Patient Input Device (RF Tablet) (50), a further Patient InputDevice (Jog Dial) (55), Glasses Cable (15), CA-VPU Cable (70), CFS-CACable (45), CFS-PTS Cable (46), Four (4) Port USB Hub (47), Mouse (60),LED Test Array (80), Archival USB Drive (49), an Isolation Transformer(not shown), adapter cables (not shown), and an External Monitor (notshown).

The external components of the Fitting System according to the presentdisclosure may be configured as follows. The battery (25) is connectedwith the VPU (20). The PTS Laptop (30) is connected to FS Laptop (10)using the CFS-PTS Cable (46). The PTS Laptop (30) and FS Laptop (10) areplugged into the Isolation Transformer (not shown) using the AdapterCables (not shown). The Isolation Transformer is plugged into the walloutlet. The four (4) Port USB Hub (47) is connected to the FS laptop(10) at the USB port. The mouse (60) and the two Patient Input Devices(50) and (55) are connected to four (4) Port USB Hubs (47). The FSlaptop (10) is connected to the Communication Adapter (CA) (40) usingthe CFS-CA Cable (45). The CA (40) is connected to the VPU (20) usingthe CA-VPU Cable (70). The Glasses (5) are connected to the VPU (20)using the Glasses Cable (15).

The present invention is a system for detecting, tracking andrecognizing human faces in a visual prosthesis. In a visual prosthesis,the input camera is always higher resolution than the electrode arrayproviding percepts to the subject. It is advantageous to detect, trackand recognize human faces. Then information can be provided to thesubject by highlighting the face in the visual scene, providing auditoror vibratory notice that a human face is in the visual scene, looking upthe face in a database to state the name of the person in the visualscene, or automatically zooming in on a face to aid the subject inidentify the face.

Referring to FIG. 4, simple face tracking can be a significant benefit ablind person. The presence of multiple faces may be also relayed. Theprocess flow of basic face detection and tracking is provided. The videoprocessor records a visual scene 102, show here with two children'sfaces. The video processor draws a square around a detected face 104.The video processor draws squares around both face units and draws asmaller square around the identifiable portions of the two faces forrecognition processing 106. Even with a very low resolution electrodearray, it is possible for a subject to locate the faces 108, to improveinteraction with the other people.

Referring to FIG. 5, square localization is a common task preformed byvisual prosthesis patients. See US Patent Application 2010/0249878, forVisual Prosthesis Fitting Training and Assessment System and Method,filed Mar. 26, 2010 which is incorporated herein by reference. Providinga square over a detected face, simplifies the face tracking to the levela square localization. In the first example 110, the face is indentifiedat an angle. It may be adventurous to straighten the square to improveuser recognition. In the second example 112 the face is outside thevisual scene so no highlight is provided. In the third example 114, theface square is simply highlighted without modification. The distance tothe person, distance direction and velocity may also be relayed to thepatent.

Referring to FIG. 6, the process of face detection begins by scanningthe input image from the camera for a pattern of face 202. There aremany well known processes for indentifying faces in an image. If a faceis detected, it is compared to a database of known faces 204. If theface is unknown, the face is cued 208 as described in greater detail inFIG. 7. If the face is known, it is announced 206 as described ingreater detail in reference to FIG. 8. Finally facial characteristicsare determined 210. Determination of facial characteristic is describedin greater detail in FIG. 9.

Referring to FIG. 7, there are several options for cueing the presenceof an unknown face which are selectable by the user. The user can changethe selection by activating controls on the VPU 20. The systemdetermines if face highlighting is selected 302, and highlights the face304. In a low resolution visual prosthesis this can be accomplishedsimply replacing the face with a bright image. In a higher resolutionvisual prosthesis this may be accomplished by marking a square or circlearound the face. Alternatively if Zoom is selected 306, the visualprosthesis zooms in on the face adding the user in indentifying the face308. If vibration is selected 310 the visual processing unit vibrates(like a cell phone in silent mode) 312. If tone is selected 314, thespeaker on the visual prosthesis emits a tone 316. Note that the cuesmay be used in combination such as highlight, vibrate and tone.

Referring to FIG. 8, the process of announcing a known face begins bydetermining if the known face has a stored vibration pattern 402. Ifthere is a stored pattern, the VPU 20 vibrates that pattern 404. It islikely that a user would only wish to have stored patterns for the mostfamiliar people as it becomes complex to remember many patterns. Theability of the VPU 20 to generate unique patterns is nearly limitless.If there is no stored pattern, the system detects if audio is on or off406. If audio is on, the speaker speaks the name of the known person408.

Referring to FIG. 9, the process of determining facial characteristicsis handled in priority order so the most pertinent information ishandled first. First the system determines if the person is near or far502. Mostly blind people wish to know if someone is in comfortablespeaking distance. So, near or far can be a simple close enough tospeak, in which case the VPU 20 speaks “near” 504, or can be an actualdistance spoken by the VPU 20. The next most important determination isif the person is facing the user or facing away 506. If the person isfacing the users, the VPU 20 speaks “facing you” 508. This can beexpanded as in the moving part of the flowchart below including facingyou, facing left, facing right, or facing away. Next the systemdetermines if the person is moving 510. The system determine if theperson is moving toward the user 512 and speaks “moving toward you” 514,is moving left 516 and speaks “moving left’ 518, is moving right 520,and speaks “moving right” 522, or is moving away 524, and speaks “movingaway” 526.

Each of the cues and announcements can be discrete or combined intophrases like “Joe, far, facing you, moving toward you”.

Stand-Alone Mode

Referring to FIG. 10, in the stand-alone mode, the video camera 13, onthe glasses 5, captures a video image that is sent to the VPU 20. TheVPU 20 processes the image from the camera 13 and transforms it intoelectrical stimulation patterns that are transmitted to the externalcoil 17. The external coil 17 sends the electrical stimulation patternsand power via radio-frequency (RF) telemetry to the implanted retinalstimulation system. The internal coil 16 of the retinal stimulationsystem receives the RF commands from the external coil 17 and transmitsthem to the electronics package 14 that in turn delivers stimulation tothe retina via the electrode array 10. Additionally, the retinalstimulation system may communicate safety and operational status back tothe VPU 20 by transmitting RF telemetry from the internal coil 16 to theexternal coil 17. The visual prosthesis apparatus may be configured toelectrically activate the retinal stimulation system only when it ispowered by the VPU 20 through the external coil 17. The stand-alone modemay be used for clinical testing and/or at-home use by the subject.

Communication Mode

The communication mode may be used for diagnostic testing,psychophysical testing, patient fitting and downloading of stimulationsettings to the VPU 20 before transmitting data from the VPU 20 to theretinal stimulation system as is done for example in the stand-alonemode described above. Referring to FIG. 9, in the communication mode,the VPU 20 is connected to the Fitting System laptop 21 using cables 70,45 and the optically isolated serial connection adapter 40. In thismode, laptop 21 generated stimuli may be presented to the subject andprogramming parameters may be adjusted and downloaded to the VPU 20. ThePsychophysical Test System (PTS) laptop 30 connected to the FittingSystem laptop 21 may also be utilized to perform more sophisticatedtesting and analysis as fully described in the related application U.S.application Ser. No. 11/796,425, filed on Apr. 27, 2007, (Applicant'sDocket No. S401-USA) which is incorporated herein by reference in itsentirety.

In one embodiment, the functionality of the retinal stimulation systemcan also be tested pre-operatively and intra-operatively (i.e. beforeoperation and during operation) by using an external coil 17, withoutthe glasses 5, placed in close proximity to the retinal stimulationsystem. The coil 17 may communicate the status of the retinalstimulation system to the VPU 20 that is connected to the Fitting Systemlaptop 21 as shown in FIG. 9.

As discussed above, the VPU 20 processes the image from the camera 13and transforms the image into electrical stimulation patterns for theretinal stimulation system. Filters such as edge detection filters maybe applied to the electrical stimulation patterns for example by the VPU20 to generate, for example, a stimulation pattern based on filteredvideo data that the VPU 20 turns into stimulation data for the retinalstimulation system. The images may then be reduced in resolution using adownscaling filter. In one exemplary embodiment, the resolution of theimage may be reduced to match the number of electrodes in the electrodearray 10 of the retinal stimulation system. That is, if the electrodearray has, for example, sixty electrodes, the image may be reduced to asixty channel resolution. After the reduction in resolution, the imageis mapped to stimulation intensity using for example a look-up tablethat has been derived from testing of individual subjects. Then, the VPU20 transmits the stimulation parameters via forward telemetry to theretinal stimulation system in frames that may employ a cyclic redundancycheck (CRC) error detection scheme.

In one exemplary embodiment, the VPU 20 may be configured to allow thesubject/patient i) to turn the visual prosthesis apparatus on and off,ii) to manually adjust settings, and iii) to provide power and data tothe retinal stimulation system. Referring again to FIGS. 1 through 4,the VPU 20 may comprise a case, and button 6 including power button forturning the VPU 20 on and off, setting button, zoom buttons forcontrolling the camera 13, temple extensions 8 for connecting to theGlasses 5, a connector port for connecting to the laptop 21 through theconnection adapter 40, indicator lights (not shown) on the VPU 20 orglasses 5 to give visual indication of operating status of the system,the rechargeable battery (not shown) for powering the VPU 20, batterylatch (not shown) for locking the battery in the case, digital circuitboards (not shown), and a speaker (not shown) to provide audible alertsto indicate various operational conditions of the system. Because theVPU 20 is used and operated by a person with minimal or no vision, thebuttons on the VPU 20 may be differently shaped and/or have specialmarkings to help the user identify the functionality of the buttonwithout having to look at it.

In one embodiment, the indicator lights may indicate that the VPU 20 isgoing through system start-up diagnostic testing when the one or moreindicator lights are blinking fast (more then once per second) and aregreen in color. The indicator lights may indicate that the VPU 20 isoperating normally when the one or more indicator lights are blinkingonce per second and are green in color. The indicator lights mayindicate that the retinal stimulation system has a problem that wasdetected by the VPU 20 at start-up diagnostic when the one or moreindicator lights are blinking for example once per five second and aregreen in color. The indicator lights may indicate that there is a lossof communication between the retinal stimulation system and the externalcoil 17 due to the movement or removal of Glasses 5 while the system isoperational or if the VPU 20 detects a problem with the retinalstimulation system and shuts off power to the retinal stimulation systemwhen the one or more indicator lights are always on and are orangecolor. One skilled in the art would appreciate that other colors andblinking patterns can be used to give visual indication of operatingstatus of the system without departing from the spirit and scope of theinvention.

In one embodiment, a single short beep from the speaker (not shown) maybe used to indicate that one of the buttons 6 have been pressed. Asingle beep followed by two more beeps from the speaker (not shown) maybe used to indicate that VPU 20 is turned off. Two beeps from thespeaker (not shown) may be used to indicate that VPU 20 is starting up.Three beeps from the speaker (not shown) may be used to indicate that anerror has occurred and the VPU 20 is about to shut down automatically.As would be clear to one skilled in the art, different periodic beepingmay also be used to indicate a low battery voltage warning, that thereis a problem with the video signal, and/or there is a loss ofcommunication between the retinal stimulation system and the externalcoil 17. One skilled in the art would appreciate that other sounds canbe used to give audio indication of operating status of the systemwithout departing from the spirit and scope of the invention. Forexample, the beeps may be replaced by an actual prerecorded voiceindicating operating status of the system.

In one exemplary embodiment, the VPU 20 is in constant communicationwith the retinal stimulation system through forward and backwardtelemetry. In this document, the forward telemetry refers totransmission from VPU 20 to the retinal stimulation system and thebackward telemetry refers to transmissions from the Retinal stimulationsystem to the VPU 20. During the initial setup, the VPU 20 may transmitnull frames (containing no stimulation information) until the VPU 20synchronizes with the Retinal stimulation system via the back telemetry.In one embodiment, an audio alarm may be used to indicate whenever thesynchronization has been lost.

In order to supply power and data to the Retinal stimulation system, theVPU 20 may drive the external coil 17, for example, with a 3 MHz signal.To protect the subject, the retinal stimulation system may comprise afailure detection circuit to detect direct current leakage and to notifythe VPU 20 through back telemetry so that the visual prosthesisapparatus can be shut down.

The forward telemetry data (transmitted for example at 122.76 kHz) maybe modulated onto the exemplary 3 MHz carrier using Amplitude ShiftKeying (ASK), while the back telemetry data (transmitted for example at3.8 kHz) may be modulated using Frequency Shift Keying (FSK) with, forexample, 442 kHz and 457 kHz. The theoretical bit error rates can becalculated for both the ASK and FSK scheme assuming a ratio of signal tonoise (SNR). The system disclosed in the present disclosure can bereasonably expected to see bit error rates of 10-5 on forward telemetryand 10-3 on back telemetry. These errors may be caught more than 99.998%of the time by both an ASIC hardware telemetry error detection algorithmand the VPU's firmware. For the forward telemetry, this is due to thefact that a 16-bit cyclic redundancy check (CRC) is calculated for every1024 bits sent to the ASIC within electronics package 14 of the RetinalStimulation System. The ASIC of the Retinal Stimulation System verifiesthis CRC and handles corrupt data by entering a non-stimulating ‘safe’state and reporting that a telemetry error was detected to the VPU 20via back telemetry. During the ‘safe’ mode, the VPU 20 may attempt toreturn the implant to an operating state. This recovery may be on theorder of milliseconds. The back telemetry words are checked for a 16-bitheader and a single parity bit. For further protection against corruptdata being misread, the back telemetry is only checked for header andparity if it is recognized as properly encoded Bi-phase Mark Encoded(BPM) data. If the VPU 20 detects invalid back telemetry data, the VPU20 immediately changes mode to a ‘safe’ mode where the RetinalStimulation System is reset and the VPU 20 only sends non-stimulatingdata frames. Back telemetry errors cannot cause the VPU 20 to doanything that would be unsafe.

The response to errors detected in data transmitted by VPU 20 may beginat the ASIC of the Retinal Stimulation System. The Retinal StimulationSystem may be constantly checking the headers and CRCs of incoming dataframes. If either the header or CRC check fails, the ASIC of the RetinalStimulation System may enter a mode called LOSS OF SYNC 950, shown inFIG. 10 a. In LOSS OF SYNC mode 950, the Retinal Stimulation System willno longer produce a stimulation output, even if commanded to do so bythe VPU 20. This cessation of stimulation occurs after the end of thestimulation frame in which the LOSS OF SYNC mode 950 is entered, thusavoiding the possibility of unbalanced pulses not completingstimulation. If the Retinal Stimulation System remains in a LOSS OF SYNCmode 950 for 1 second or more (for example, caused by successive errorsin data transmitted by VPU 20), the ASIC of the Retinal StimulationSystem disconnects the power lines to the stimulation pulse drivers.This eliminates the possibility of any leakage from the power supply ina prolonged LOSS OF SYNC mode 950. From the LOSS OF SYNC mode 950, theRetinal Stimulation System will not re-enter a stimulating mode until ithas been properly initialized with valid data transmitted by the VPU 20.

In addition, the VPU 20 may also take action when notified of the LOSSOF SYNC mode 950. As soon as the Retinal Stimulation System enters theLOSS OF SYNC mode 950, the Retinal Stimulation System reports this factto the VPU 20 through back telemetry. When the VPU 20 detects that theRetinal Stimulation System is in LOSS OF SYNC mode 950, the VPU 20 maystart to send ‘safe’ data frames to the Retinal Stimulation System.‘Safe’ data is data in which no stimulation output is programmed and thepower to the stimulation drivers is also programmed to be off. The VPU20 will not send data frames to the Retinal Stimulation System withstimulation commands until the VPU 20 first receives back telemetry fromthe Retinal Stimulation System indicating that the Retinal StimulationSystem has exited the LOSS OF SYNC mode 950. After several unsuccessfulretries by the VPU 20 to take the implant out of LOSS OF SYNC mode 950,the VPU 20 will enter a Low Power Mode (described below) in which theimplant is only powered for a very short time. In this time, the VPU 20checks the status of the implant. If the implant continues to report aLOSS OF SYNC mode 950, the VPU 20 turns power off to the RetinalStimulation System and tries again later. Since there is no possibilityof the implant electronics causing damage when it is not powered, thismode is considered very safe.

Due to an unwanted electromagnetic interference (EMI) or electrostaticdischarge (ESD) event the VPU 20 data, specifically the VPU firmwarecode, in RAM can potentially get corrupted and may cause the VPU 20firmware to freeze. As a result, the VPU 20 firmware will stop resettingthe hardware watchdog circuit, which may cause the system to reset. Thiswill cause the watchdog timer to expire causing a system reset in, forexample, less than 2.25 seconds. Upon recovering from the reset, the VPU20 firmware logs the event and shuts itself down. VPU 20 will not allowsystem usage after this occurs once. This prevents the VPU 20 code fromfreezing for extended periods of time and hence reduces the probabilityof the VPU sending invalid data frames to the implant.

Supplying power to the Retinal stimulation system can be a significantportion of the VPU 20's total power consumption. When the Retinalstimulation system is not within receiving range to receive either poweror data from the VPU 20, the power used by the VPU 20 is wasted.

Power delivered to the Retinal stimulation system may be dependent onthe orientation of the coils 17 and 16. The power delivered to theRetinal stimulation system may be controlled, for example, via the VPU20 every 16.6 ms. The Retinal stimulation system may report how muchpower it receives and the VPU 20 may adjust the power supply voltage ofthe RF driver to maintain a required power level on the Retinalstimulation system. Two types of power loss may occur: 1) long term (>˜1second) and 2) short term (<˜1 second). The long term power loss may becaused, for example, by a subject removing the Glasses 5.

In one exemplary embodiment, the Low Power Mode may be implemented tosave power for VPU 20. The Low Power Mode may be entered, for example,anytime the VPU 20 does not receive back telemetry from the Retinalstimulation system. Upon entry to the Low Power Mode, the VPU 20 turnsoff power to the Retinal stimulation system. After that, andperiodically, the VPU 20 turns power back on to the Retinal stimulationsystem for an amount of time just long enough for the presence of theRetinal stimulation system to be recognized via its back telemetry. Ifthe Retinal stimulation system is not immediately recognized, thecontroller again shuts off power to the Retinal stimulation system. Inthis way, the controller ‘polls’ for the passive Retinal stimulationsystem and a significant reduction in power used is seen when theRetinal stimulation system is too far away from its controller device.FIG. 10 b depicts an exemplary block diagram 900 of the steps taken whenthe VPU 20 does not receive back telemetry from the Retinal stimulationsystem. If the VPU 20 receives back telemetry from the Retinalstimulation system (output “YES” of step 901), the Retinal stimulationsystem may be provided with power and data (step 906). If the VPU 20does not receive back telemetry from the Retinal stimulation system(output “NO” of step 901), the power to the Retinal stimulation systemmay be turned off. After some amount of time, power to the Retinalstimulation system may be turned on again for enough time to determineif the Retinal stimulation system is again transmitting back telemetry(step 903). If the Retinal stimulation system is again transmitting backtelemetry (step 904), the Retinal stimulation system is provided withpower and data (step 906). If the Retinal stimulation system is nottransmitting back telemetry (step 904), the power to the Retinalstimulation system may again be turned off for a predetermined amount oftime (step 905) and the process may be repeated until the Retinalstimulation system is again transmitting back telemetry.

In another exemplary embodiment, the Low Power Mode may be enteredwhenever the subject is not wearing the Glasses 5. In one example, theGlasses 5 may contain a capacitive touch sensor (not shown) to providethe VPU 20 digital information regarding whether or not the Glasses 5are being worn by the subject. In this example, the Low Power Mode maybe entered whenever the capacitive touch sensor detects that the subjectis not wearing the Glasses 5. That is, if the subject removes theGlasses 5, the VPU 20 will shut off power to the external coil 17. Assoon as the Glasses 5 are put back on, the VPU 20 will resume poweringthe external coil 17. FIG. 10 c depicts an exemplary block diagram 910of the steps taken when the capacitive touch sensor detects that thesubject is not wearing the Glasses 5. If the subject is wearing Glasses5 (step 911), the Retinal stimulation system is provided with power anddata (step 913). If the subject is not wearing Glasses 5 (step 911), thepower to the Retinal stimulation system is turned off (step 912) and theprocess is repeated until the subject is wearing Glasses 5.

One exemplary embodiment of the VPU 20 is shown in FIG. 11. The VPU 20may comprise: a Power Supply, a Distribution and Monitoring Circuit(PSDM) 1005, a Reset Circuit 1010, a System Main Clock (SMC) source (notshown), a Video Preprocessor Clock (VPC) source (not shown), a DigitalSignal Processor (DSP) 1020, Video Preprocessor Data Interface 1025, aVideo Preprocessor 1075, an I²C Protocol Controller 1030, a ComplexProgrammable Logic device (CPLD) (not shown), a Forward TelemetryController (FTC) 1035, a Back Telemetry Controller (BTC) 1040,Input/Output Ports 1045, Memory Devices like a Parallel Flash Memory(PFM) 1050 and a Serial Flash Memory (SFM) 1055, a Real Time Clock 1060,an RF Voltage and Current Monitoring Circuit (VIMC) (not shown), aspeaker and/or a buzzer, an RF receiver 1065, and an RF transmitter1070.

The Power Supply, Distribution and Monitoring Circuit (PSDM) 1005 mayregulate a variable battery voltage to several stable voltages thatapply to components of the VPU 20. The Power Supply, Distribution andMonitoring Circuit (PSDM) 1005 may also provide low battery monitoringand depleted battery system cutoff. The Reset Circuit 1010 may havereset inputs 1011 that are able to invoke system level rest. Forexample, the reset inputs 1011 may be from a manual push- button reset,a watchdog timer expiration, and/or firmware based shutdown. The SystemMain Clock (SMC) source is a clock source for DSP 1020 and CPLD. TheVideo Preprocessor Clock (VPC) source is a clock source for the VideoProcessor. The DSP 1020 may act as the central processing unit of theVPU 20. The DSP 1020 may communicate with the rest of the components ofthe VPU 20 through parallel and serial interfaces. The Video Processor1075 may convert the NTSC signal from the camera 13 into a down-scaledresolution digital image format. The Video Processor 1075 may comprise avideo decoder (not shown) for converting the NTSC signal intohigh-resolution digitized image and a video scaler (not shown) forscaling down the high-resolution digitized image from the video decoderto an intermediate digitized image resolution. The video decoder may becomposed of an Analog Input Processing, Chrominance and LuminanceProcessing and Brightness Contrast and Saturation (BSC) Controlcircuits. The video scaler may be composed of Acquisition control,Pre-scaler, BSC-control, Line Buffer and Output Interface. The I²CProtocol Controller 1030 may serve as a link between the DSP 1020 andthe I²C bus. The I²C Protocol Controller 1030 may be able to convert theparallel bus interface of the DSP 1020 to the I²C protocol bus or viceversa. The I²C Protocol Controller 1030 may also be connected to theVideo Processor 1075 and the Real Time Clock 1060. The VPDI 1025 maycontain a tri-state machine to shift video data from Video Preprocessor1075 to the DSP 1020. The Forward Telemetry Controller (FTC) 1035 packs1024 bits of forward telemetry data into a forward telemetry frame. TheFTC 1035 retrieves the forward telemetry data from the DSP 1020 andconverts the data from logic level to biphase marked data. The BackTelemetry Controller (BTC) 1040 retrieves the biphase marked data fromthe RF receiver 1065, decodes it, and generates the BFSR, BCLKR and BDRfor the DSP 1020. The Input/Output Ports 1045 provide expanded IOfunctions to access the CPLD on-chip and off-chip devices. The ParallelFlash Memory (PFM) 1050 may be used to store executable code and theSerial Flash Memory (SFM) 1055 may provide Serial Port Interface (SPI)for data storage. The VIMC may be used to sample and monitor RFtransmitter 1070 current and voltage in order to monitor the integritystatus of the retinal stimulation system.

Accordingly, what has been shown is an improved method making a hermeticpackage for implantation in a body. While the invention has beendescribed by means of specific embodiments and applications thereof, itis understood that numerous modifications and variations could be madethereto by those skilled in the art without departing from the spiritand scope of the invention. It is therefore to be understood that withinthe scope of the claims, the invention may be practiced otherwise thanas specifically described herein.

1. A method of aiding a visual prosthesis subject comprising: detectinga face in the subject's visual scene; and providing cues to the subjectregarding a detected face.
 2. The method of claim 1, wherein the cue isa sound.
 3. The method of claim 1, wherein the cue is a vibration. 4.The method of claim 1, wherein the cue is stating a name associated withthe detected face.
 5. The method according to claim 4, furthercomprising looking up the face in a look up table to retrieve the nameassociated with the detected face.
 6. The method of claim 1, wherein thecue is highlighting the detected face.
 7. The method of claim 1, whereinthe cue is zooming in on the detected face.
 8. The method of claim 1,wherein the cue includes an indication of if the face is looking towardthe subject or turned away.
 9. The method of claim 1, wherein the cue istactile feedback.
 10. The method of claim 1, further comprisingdetecting facial characteristic.
 11. The method of claim 10, wherein thecharacteristic is gender.
 12. The method of claim 10, wherein thecharacteristic is size.
 13. The method of claim 10, wherein thecharacteristic is distance.
 14. The method of claim 10, wherein thecharacteristic is head movement.
 15. The method of claim 10, wherein thecharacteristic is motion.
 16. A visual prosthesis comprising: a camerasensing a visual scene; a video processing unit receiving data of thevideo scene from the camera; and an implanted neural stimulatorreceiving data of the visual scene from the video processor and suitablestimulate visual neural tissue to induce the perception of sight;wherein the video processing unit includes a face detection circuit. 17.The visual prosthesis according to claim 16, further comprising controlson the video processing unit to control the face detection circuit. 18.The visual prosthesis according to claim 16, further comprising aspeaker on the video processing unit activated by the faced detectioncircuit.
 18. The visual prosthesis according to claim 16, furthercomprising a vibration unit in the video processing unit activated bythe face detection circuit.
 19. The visual prosthesis according to claim16, further comprising a look up table including information associatingnames and faces.
 20. The visual prosthesis according to claim 16,further comprising a detection circuit for detecting facialcharacteristics associated with the face detection circuit.